1. Field of the Invention
The present invention relates to an ink jet printing method, and in particular, to an ink jet printing apparatus and an ink jet printing method in which a predetermined area is printed by two reciprocating scans.
2. Description of the Related Art
In some ink jet printing apparatuses for color printing, print heads that eject a cyan ink, a magenta ink, and a yellow ink, respectively, are arranged in a main scanning direction. It is assumed that these print heads are used to carry out reciprocating 2-pass printing. Then, when the magenta ink and the yellow ink are focused on, during the first forward scan, the nozzles in the lower half of each relevant print head are used to print an image at a duty of about 50% so that the yellow ink and then the magenta ink are printed. Then, the sheet is fed by a length equal to the half of the width of the print head. Then, during the second backward scan, the nozzles in the upper half of each relevant print head are used to print an image at a duty of about 50% so that the yellow ink and then the magenta ink are printed. The first and second reciprocating scans allow one band with a width equal to the half of the print head width to be completely printed. In one band in such printing, printing is carried out in the following order: magenta, yellow, yellow, and magenta. In the adjacent band, printing is carried out in the following order: yellow, magenta, magenta, and yellow. As a result, the resultant color may vary among bands each completed by two-pass printing depending on the first ink used for printing.
A printing method is known in which the ink colors are printed is in the same order in order to reduce the above-described difference in color among the bands depending on the order of printing of the colors (for example, refer to Japanese Patent No. 3176130). In this printing method, conveyance of a print medium following a forward print scan differs, in direction and amount, from conveyance of the print medium following a backward print scan so as to allow the ink colors to be printed in the same order. This reduces the variation in color among the bands.
In the printing method described in Japanese Patent No. 3176130, the first band is completely printed by the first scan and the second scan, whereas the second band is completely printed by the first scan and the fourth scan. Thus, the first band and the second band vary in the duration from the end the first scan until the beginning of the second scan during the two passes for printing the band. Such a time difference may lead to time difference unevenness among the bands.